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How to do the completing the square in quadratic equation? Please answer x^2+5x=11

Sagot :

Kaiusidn
We are given the equation x^2 + 5x + D = 11 + D. In this equation, A is 1, B is 5 and C is 11. Now, we divide B (which is 5) by 2, square it and multiply with A to get D: (5/2)^2 = 25/4 --> x^2 + 5x + (25/4) = 11 + (25/4) --> Factor the quad. equation: (x - (5/2))(x - (5/2)) = 69/4 --> (x - (5/2))^2 - 69/4 = 0.
Riza1idn
[tex]x^2+5x=11 \\\\x^2+5x-11 =0 \\ \\ a=1, \ b=5 , \ \ c=-11\\ \\ x = \frac{-b\pm \sqrt{b^2-4ac}}{2a} \\ \\ x_{1} = \frac{-5 -\sqrt{5^2-4 \cdot 1 \cdot (-11)}}{2 \cdot 1} =\frac{-5-\sqrt{25+44}}{2} =\frac{-5-\sqrt{69}}{2} \approx \frac{-5-8,3}{2} \approx -\frac{13,3}{2} \approx -6,65[/tex]

[tex]x_{2} = \frac{-5+\sqrt{5^2-4 \cdot 1 \cdot (-11)}}{2 \cdot 1} =\frac{-5+\sqrt{25+44}}{2} = \frac{-5+\sqrt{69}}{2} \approx \frac{-5+8,3}{2} \approx \frac {3,3}{2} \approx 1,65[/tex]